Noise-induced asymmetries limits, as a function of the S/N, of the difference in velocity between the peak and selected bisector levels (in percentage of the intensity peak, as indicated in the plot) for V500 CALIFA spectra derived from a large number of modeled single-Gaussian profiles. The ΔV_b obtained for each selected bisector level are within the curves for that bisector. Any ΔV_b beyond these curves should be indicating the presence of secondary gaseous components.